1. Field of the Invention
The present invention relates to a zero-valent transition metal complex and method for producing an organometallic compound using the same as a starting material, more particularly a zero-valent transition metal complex which can be used for producing a catalyst usable for producing a polyolefin by ring-opening metathesis polymerization of an olefin and an epothilone by ring-closing metathesis reaction, and a method for efficiently producing, at a low cost, an organometallic compound useful as a catalyst, using the zero-valent transition metal complex as a starting material.
2. Description of the Prior Art
Reactions proceeding in the presence of a transition metal compound have been widely used for producing various products from those of low-molecular-weight, e.g., medicines, to those of high-molecular-weight, e.g., highly functional plastics, by virtue of the catalytic actions which the complex from the transition metal compound provides.
The well-known reactions include polymerization of polyethylene or polypropylene in the presence of a Ziegler-Natta catalyst comprising titanium tetrachloride or trichloride and alkyl aluminum, polymerization of homogeneous polyolefin in the presence of a Kaminski catalyst comprising zirconocene and methyl aluminoxane, and organic metathesis reactions in the presence of a transition metal carbene catalyst.
Recently, transition metal carbene catalysts, in particular ruthenium carbene catalysts, have been attracting attention. A ruthenium carbene catalyst is composed of a compound having the Ru═C bond (which holds a ruthenium atom and chargeless, divalent carbon atom). In particular, dichloro-phenylcarbene-bis-(tricyclohexyl phosphine)ruthenium, represented by [(Cl2Ru═CHPh)(PCy3)2], is developed and disclosed by the Grubbs group of California Institute of Technology (refer to JP-A-11-510807, claims and the like and JP-A-11-262667, claims and the like).
It has been clearly demonstrated that the compound exhibits excellent catalytic activity for metathesis without been deactivated even in the presence of moisture or oxygen, and showing resistance to a functional group in a metathesis reaction substrate. As such, it has been widely used for various industrial purposes, e.g., ring-closing metathesis synthesis of various olefins to produce medicines or the like; and ring-opening polymerization of norbornene-based monomers, beginning with dicyclopentadiene as a representative starting monomer for metathesis polymerization, to produce formed articles of excellent characteristics with respect to mechanical strength, heat resistance and dimensional stability, among others, where the reaction is carried out in a mold in a reaction injection molding process or the like, and hence attracting attention.
The catalyst exhibits its catalytic activity not coming from its reactions with an alkyl metal or the like to activate the catalyst in the system but from the inherent activity of the single complex itself. This causes problems resulting from dispersibility or the like of the catalyst being a rate-determining step, because the reactions of a metathesis-reactive monomer start as soon as it comes into contact with the catalyst. This may cause crucial problems in polymerization of cross-linkable monomer, e.g., dicyclopentadiene. These problems include severe limitations imposed on the process operation and fluctuations of the polymer product properties.
A method for retarding the polymerization by incorporating triphenyl phosphine or the like is generally known to solve the above problems. This, however, may cause problems related to product safety, resulting from contamination of the system with phosphorus or the like.
Dichloro-phenylcarbene-bis-(tricyclohexyl phosphine)ruthenium, represented by [(Cl2Ru═CHSPh)(PCy3)2], is proposed as a catalyst which can solve the above problems (refer to, e.g., JP-A-2002-506452, claims and the like). The compounds of the above formula with sulfur atom substituted by oxygen atom, or imino or phosphine-diyl group are also disclosed by JP-A-2002-506452.
This catalyst, although excellent, involves process-related problems. For example, JP-A-2002-506452 discloses its synthesis methods a) and b) in EXAMPLE 1 (page 52). The method a) needs a starting material which itself has a complex chemical structure of RuCl2[P(C6H11)3]2(═CH—C6H5) and hence a time-consuming process for its synthesis. On the other hand, the method b) uses ruthenium dichloride (cis,cis-cyclooctadiene) as a starting material, which itself is a compound of simple chemical structure. However, it needs a complex process for production of the target product, comprising reaction of the above compound with complex-structure compounds of 1,8-diazabicyclo[5.4.0]undeca-7-ene and tricyclohexyl phosphine in isopropanol at 80° C. for 1 hour, and incorporation of the effluent, after it is cooled at −20° C. for 1 hour, with a 1 mol/L diethyl ether hydrochloride solution with stirring for 15 minutes and further with 1-hexine and phenyl vinyl sulfide. Therefore, the process needs massive quantities of expensive starting materials and several steps, and hence is time-consuming and disadvantageous costwise.
Under these circumstances, the inventors of the present invention have studied synthesis of heterocarbene complexes, e.g., RuCl2[P(C6H11)3]2(═CH—S—), and proposed a method for synthesizing a heterocarbene complex efficiently at a low cost using a starting material of relatively simple chemical structure (as disclosed by JP-A-2003-286295) as an alternative for the conventional method based on vinyl exchanging.
However, this method involves a problem of limited production yield, when the starting material of relatively simple chemical structure, i.e., a zero-valent transition metal complex (e.g., ruthenium(cymene)(1,5-cyclooctadiene) is to be synthesized on a commercial scale. Increasing the yield needs iteration of extraction cycles, which makes the process complex and disadvantageous costwise.